The invention relates to a selective hydrogenation process for producing aminonitriles from corresponding dinitriles in the presence of one or more additives that improve the yield of and/or selectivity to the aminonitrile.
Aminonitriles are a class of important chemicals that have a variety of industrial applications. For example, aminonitriles can be used as monomers for producing high molecular weight polyamides. Specifically, 6-aminocapronitrile can be used to produce nylon 6.
Aminonitriles can be produced by catalytic partial hydrogenation of dinitriles. See, for example, U.S. Pat. No. 2,208,598, U.S. Pat. No. 2,257,814, U.S. Pat. No. 2,762,835, U.S. Pat. No. 3,322,815, U.S. Pat. No. 3,350,439, U.S. Pat. No. 3,591,618, U.S. Pat. No. 4,389,348, U.S. Pat. No. 4,601,859, U.S. Pat. No. 5,151,543, U.S. Pat. No. 5,296,628, U.S. Pat. No. 5,512,697, U.S. Pat. No. 5,527,946, DE836938, DE848654, DE-A-19636768 and WO99/47492, all of which are incorporated by reference herein for all purposes as if fully set forth. However, the yield of and selectivity to a desired aminonitrile using some of the known processes may not be as high as desired, and the amount of the complete hydrogenation product (diamine) is also generally higher than desired.
WO99/47492 mentioned above describes the use of certain carbonyl group-containing compounds as additives in the partial hydrogenation process to improve the yield of and/or selectivity to the desired aminonitrile product, and/or reduce the amount of fully hydrogenated product (diamine) produced.
We have now found new classes of compounds that also effectively function as improved yield and/or selectivity additives in the partial hydrogenation processes such as, for example, those mentioned in previously incorporated WO99/47492.
In accordance with one aspect of the present invention, there is provided a process for the partial hydrogenation of a dinitrile to an aminonitrile, comprising the step of contacting the dinitrile with a hydrogen-containing fluid in the presence of (a) a solvent comprising liquid ammonia, an alcohol, or both; (b) a hydrogenation catalyst; and (c) an additive for improving the yield of and/or selectivity to the aminonitrile, characterized in that the additive comprises a compound selected from the group consisting of:
carbon monoxide;
a tetraalkylammonium hydroxide compound;
a tetraalkylphosphonium hydroxide compound;
a multi-centered metal carbonyl cluster;
an organic isonitrile;
a cyanide compound having at least one cyano group bound to other than a carbon atom; and
a fluoride compound.
Another aspect of the present invention relates to a process for improving the yield of and/or selectivity to an aminonitrile obtained by partially hydrogenating a corresponding dinitrile with a hydrogen-containing fluid in the presence of a solvent and a hydrogenation catalyst, comprising the step of partially hydrogenating the dinitrile in the further presence of an effective amount of an additive comprising a compound selected from the group consisting of:
carbon monoxide;
a tetraalkylammonium hydroxide compound;
a tetraalkylphosphonium hydroxide compound;
a multi-centered metal carbonyl cluster;
an organic isonitrile;
a cyanide compound having at least one cyano group bound to other than a carbon atom; and
a fluoride compound.
In yet another aspect of the present invention, there is provided a catalyst composition comprising a combination of (1) a hydrogenation catalyst suitable for hydrogenating a dinitrile to an aminonitrile; and (2) an additive that improves the yield of and/or selectivity to the aminonitrile from said catalyst under hydrogenation conditions, characterized in that the additive comprises a compound selected from the group consisting of:
carbon monoxide;
a tetraalkylammonium hydroxide compound;
a tetraalkylphosphonium hydroxide compound;
a multi-centered metal carbonyl cluster;
an organic isonitrile;
a cyanide compound having at least one cyano group bound to other than a carbon atom; and
a fluoride compound.
An advantage of this invention is that an aminonitrile can be produced in higher yield and/or having a higher selectivity to the aminonitrile with the additive than without. Other objects and advantages will become more apparent as the invention is more fully disclosed herein below.